Method of producing locally occurring infrasound

ABSTRACT

Two spaced directional acoustical transducers are directed towards a common point so that the acoustical waves produced thereby intersect throughout a given area. By utilizing a frequency difference between the acoustical waves of less than 20 Hz., or by propagating the acoustical waves at the same frequency while phase modulating one of them at less than 20 Hz., resultant acoustical waves of less than 20 Hz. are produced in the area of intersection.

United States Patent Inventor William T. Clark, 111

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[56] Relerences Cited UNITED STATES PATENTS 1,616,639 2/1927 Sprague181/0.5 J 1,951,669 3/1934 Ramsey l81/0.5 J 3,398,810 8/1968 Clark .118l/0.5 J

Primary ExaminerMa1colm F. Hubler Attorney-James H. Littlepage ABSTRACT:Two spaced directional acoustical transducers are directed towards acommon point so that the acoustical waves produced thereby intersectthroughout a given area. By utilizing a frequency difference between theacoustical waves of less than 20 Hz., or by propagating the acousticalwaves at the same frequency while phase modulating one of them at lessthan 20 Hz., resultant acoustical waves of less than 20 Hz. are producedin the area of intersection.

PATENTED 0m 1 2 IHYI 8.612.211

Inmulllunlmnlllumnlmlmfiuu HJUWJU lllllllilllliHlllmH "mmnmmwhnn 1 I22W/ I I lNVENTOR WlLLIA T. CLARKJI ATTORNEY METHOD OF PRODUCING LOCALLYOCCURRING INFRASOUND FIELD OF INVENTION Acoustical Systems,Miscellaneous.

PRIOR ART Sprague U.S. Pat. No. 1,616,639; Ramsey U.S. Pat. No.l,75l,667; Clark, III U.S. Pat. No. 3,398,810; lnfrasound by V. Gavreau,Science Journal, Jan. 1968.

OBJECTS It isknown that infrasound, i.e., inaudible acoustical waves ofless than Hz. can have physiological and neurophysiological effects, andexperimental data indicates that those in the range of 5 Hz. to 7 llzucan effectthe alpha wave pattern of the human brain. Experimentationwith infrasound has been difficult and dangerous. The length of thesewaves is so great that extremely large baffles, chambers or whistleshave heretofore been necessary to produce them. Their omnidirectionalcharacteristics result in great power losses, since the wave energy froma source is dissipated over a wide area, and it has been difficult, ifnot impossible, to focus the wave energy on a subject under test; andbecause of this, the experimenter, as well as the subject, is oftentimessubjected to the same forces, which might be deleterious. Because of theeffects of these waves on the human body and brain, it has beentheorized that infrasound might be useful in warfare because it cannotbe detected by the human ear, and it has a potential for harming ordemobilizing an enemy subjected to it.

The object of this invention is to provide a method and apparatus forproducing infrasound utilizing two highly directional acoustical wavesources propagating intersecting beams of sound waves at a frequencywhich may be in the audible range or above, and which waves in and ofthemselves, because of their frequencies which are higher thaninfrasound, do not have the same physiological or neurophysiologicaleffects on a subject in their individual paths but which, in their areasof intersection, combine or beat against one another to produceresultant waves in the infrasonic range. A further object is to providea system for producing infrasound, but utilizing extremely small sourcesfor the infrasound energy as compared with previously available sources.

These and other objects will be apparent from the followingspecification and drawing, in which:

FIG. I is a diagram illustrating the principle of intersecting beams ofacoustical waves;

FIG. 2 is a wave diagram illustrating the simple heterodyne principlewhich may be utilized for producing an infrasonic beat;

FIG. 3 is a wave diagram illustrating the phase shift principle whichmay be utilized for producing an infrasonic resultant:

FIG. 4 is a-simplified circuit diagram ofa system for producing andpropagating the heterodyning waves diagrammed in Fig. 2; and,

FIG. 5 is a simplified circuit diagram of a system for producing andpropagating acoustical waves, one of which is phase modulated asdiagrammed in Fig. 3.

Referring first to FIG. I, there are diagrammatically illustrated twoacoustical transducers, which may be pneumatic whistles oroscillatondriven electrical transducers, each producing a directionalbeam 6 and 8, respectively. The beams intersect in area 10. If the wavesin the beams are above the audible range, and if they are of fixedamplitude, and if they are of different frequencies or if they are ofthe same frequency and one is phase modulated, then a beat or resultantfrequency is produced in the area of intersection. This, broadly, is thetheory of the system disclosed in my prior U.S. Pat. No. 3,398,810,except that an audible signal was there produced in the area ofintersection, and there was no concept of producing physiological orneurophysiolo'gical effects in localized areas.

The infrasound produced by intersecting waves in beams 6 and 8 may beproduced in various ways. For example, referring to Fig. 2, let it beassumed that the frequency of waves 12 in beam 6 is 30,000 l-Iz., and ofconstant amplitude, and the frequency of waves 14 in beam 8 is 29,995Hz., also at constant amplitude. When the two waves intersect, a beatfrequency of 5 Hz. results. Also, two waves, either or both of which areat audible frequencies, could be used if inaudibility were of noimportance. 2

While amplitude modulation of the waves in one beam may be desirable insome applications, if inaudibility in the amplitude modulated beam pathis not important, it is essential that the amplitude of the wave inneither beam shall be varied at an infrasonic rate, since then aninfrasonic pressure wave would be set up at the source of propagation,and this would produce the undesired effects of power loss,nondirectivity, and danger to the operator.

The diagram of Fig. 3 illustrates the utilization of two waves 18 and20, both of the same frequency and amplitude, but with phase-shifting ofwave 18 so as to produce a resultant acoustical signal 20 of 5 Hz. inthe area of intersection. When the in-phase components meet at theintersection, they will add, and out-of-phase components will subtract;and anything in between will add or subtract to a greater or lesserdegree. Such addition or subtraction constitutes a compression orrarification of the atmosphere, thereby producing infrasonic waves atthe intersection. Similar phase or frequency modulation may be used toproduce a warble infrasonic wave at the intersection; for example, aninfrasonic, wave that varies, for example, between 5 and 7 l-Iz.,instead of a steady tone, so as to "bracket" the normal alpha wavefrequency of a human subject in the area of intersection. The infrasonicwave may also be pulsed" by the use of phase or frequency modulation, solong as the amplitude of the waves in neither transmitted beam arevaried at an infrasonic rate; and methods for eliminating such variationshould be employed.

Suitable means for accomplishing the above results will suggestthemselves to those skilled in the art. For example, Fig. 4 is anelementary circuit and block diagram of a system utilizing a transistoroscillator circuit 24 tuned, for example, to 30,000 Hz., anothertransistor oscillator 26 tuned to 29,995 I-Iz., and power amplifiers 28and 30 between the oscillators and their respective transducers 2 and 4.

Fig. 5 is an elementary circuit and block diagram of a system suitableto achieve the objectives of Fig. 3. This system utilizes a masteroscillator 32 which feeds a signal of fixed frequency and amplitude totransducer 2 through a power amplifier 34. Master oscillator 32 alsosupplies a similar signal to a phase modulator 36 through a bufferamplifier 38, which assures that the modulated and unmodulated channelsare kept electrically separate.

Controlling phase modulator 36 is a source of infrasound signal 40 whichdrives the phase modulator in the same manner that an audio signal woulddrive the phase modulation, but a frequency of, for example 5 Hz. Thesignal from phase modulator 36 is fed to transducer 4 via poweramplifier 42. In both systems, infrasound is produced in the areas 10 ofintersection of the two signals.

While the invention described in the foregoing specification has obviousutility for laboratory experimentation, it may also have utility as amilitary weapon or for riot control, and it may be useful for submarinewarfare, in which case intersecting beams could be transmitted throughthe water and a bull to occupants inside. Also, it is believed thatinfrasound may influence earthquakes and land mass movement and fault,as well as atmospheric conditions.

lclaim:

l. The method of creating infrasound waves in a localized region, whichmethod comprises,

transmitting from two spaced points a pair of intersecting beams ofacoustical signal waves both being devoid of amplitude modulation at arate of less than 20 Hz. and both higher in frequency than 20 I-lz.,

and creating in the region of intersection of said beams infrasonicacoustical waves as a result of additive and substractive effects of theintersecting wave fronts of said acoustical signal waves.

2. The method recited in claim 1, wherein the waves in one of said beamsare transmitted at a substantially constant frequency and the waves inthe other of said beams are transmitted at another constant frequencywhich differs from the frequency of the first-mentioned frequency byless than 20 Hz.

3. The method recited in claim 2, wherein the differences in frequencybetween the waves in the two beams is in the range of5 Hz. to 7 Hz.

4. In the method recited tn claim 3, the step of regularly shifting thedifference in frequency between the two beams between 5 Hz. and 7 Hz. toproduce an infrasonic warble signal in the area of intersection.

5. The method recited in claim 1, wherein the waves in both of saidbeams are transmitted at substantially the same frequency, and whereinthe waves of one of the beams is phase-modulated by a signal with afrequency of less than 20 Hz.

6. The method as recited in claim 5, wherein the phase modulating signalis in the order of 5 Hz. to 7 Hz.

7. The method recited in claim 6, wherein the phase modulating signalregularly varies between 5 Hz. and 7 Hz. to produce an infrasonic warblesignal in the area of intersection.

1. The method of creating infrasound waves in a localized region, whichmethod comprises, transmitting from two spaced points a pair ofintersecting beams of acoustical signal waves both being devoid ofamplitude modulation at a rate of less than 20 Hz. and both higher infrequency than 20 Hz., and creating in the region of intersection ofsaid beams infrasonic acoustical waves as a result of additive andsubstractive effects of the intersecting wave fronts of said acousticalsignal waves.
 2. The method recited in claim 1, wherein the waves in oneof said beams are transmitted at a substantially constant frequency andthe waves in the other of said beams are transmitted at another constantfrequency which differs from the frequency of the first-mentionedfrequency by less than 20 Hz.
 3. The method recited in claim 2, whereinthe differences in frequency between the waves in the two beams is inthe range of 5 Hz. to 7 Hz.
 4. In the method recited tn claim 3, thestep of regularly shifting the difference in frequency between the twobeams between 5 Hz. and 7 Hz. to produce an infrasonic warble signal inthe area of intersection.
 5. The method recited in claim 1, wherein thewaves in both of said beams are transmitted at substantially the samefrequency, and wherein the waves of one of the beams is phase-modulatedby a signal with a frequency of less than 20 Hz.
 6. The method asrecited in claim 5, wherein the phase modulating signal is in the orderof 5 Hz. to 7 Hz.
 7. The method recited in claim 6, wherein the phasemodulating signal regularly varies between 5 Hz. and 7 Hz. to produce aninfrasonic warble signal in the area of intersection.